This invention relates to cured coatings, and more particularly to curable acrylate coating compositions, their use, and coated articles resulting therefrom.
Coating polymeric resin substrates such as, for example, articles of molded polycarbonate, polyester, polyurethane and the like to improve their resistance to weathering is an accepted procedure. Such coatings may include radiation curable polyacrylic or polyacrylic-urethane coatings.
Conventionally cured hardcoat finishes have several disadvantages. In general, the coating materials and the curing agent must be applied separately, in a particular sequence and at particular relative levels as both the proportions of the ingredients and the timing of their application is critical. Therefore conventionally cured hardcoats have been difficult and costly to apply, especially with the consistency and uniformity required in current commercial applications. Curable coatings have been used to try and overcome several of those disadvantages. In particular, curable coating compositions may be premixed, e.g. the polymerization initiator may be added to the active ingredients when the coating is produced, and not by the user when the coating is applied. Thus, mixing and measurement errors can be avoided and a more consistent product can be obtained.
However the curable coating compositions themselves pose various problems. For example, typical UV hardcoats are high molecular weight, highly crosslinked films, which are formed from the highly reactive acrylate functionality. As such, known UV hardcoats have suffered from limited durability, and their low solids content and cured resin shrinkage. Also high amounts of UV light are required to cure. In addition the hardcoats formulated in an attempt to overcome these problems typically suffer from some combination of loss of abrasion and scratch resistance, poor adhesion, poor processibility and unsatisfactory durability.
A need therefore exists for a curable product which is conveniently processable and which forms cured coatings exhibiting improved physical and chemical properties, e.g. scratch and abrasion resistance, adhesion and durability. The present invention provides novel solutions to these and similar problems associated with the method of making and use of curable coatings.